TFT Nasus Ultimate?
I think if Nasus gets added to TFT, he should have a relatively low mana pool (maybe 75) and his ultimate does very little damage at the start of the round, BUT every time he uses it, his ultimate damage scales super hard, .. potentially doubles every time.
Edit: I forgot to say that by "ultimate" I mean his Q. The doubling damage would make it function like his stacks. A long round would be like late game and he would one-shot anyone, if it goes too long.